1. Field of the Invention
The present invention relates generally to the art of site production of concrete and, more particularly, is concerned with a system incorporating improved features for facilitating more efficient, problem-free and versatile production of concrete.
2. Description of the Prior Art
It is accepted practice today to produce concrete at the job site where it is to be used, and as it is used, by employment of a complete concrete production plant mounted on a truck or other suitable chassis. One type of mobile concrete production plant which has achieved widespread commercial acceptance is the ZIM-MIXER system, which was originally illustrated and described in U.S. Pat. No. 3,310,293 to Harold M. Zimmerman.
The ZIM-MIXER mobile concrete production system includes a storage tank mounted on the chassis bed which has two longitudinally extending hoppers separated by a common wall. One hopper contains sand, and the other contains gravel or stone. A central, longitudinal conveyor operatively mounted along a bottom trough common to both hoppers receives sand and stone and delivers the materials to a rear discharge end. Also, the system includes a separate cement hopper as well as a separate water tank mounted on the chassis. Cement is dispensed in the desired proportion by a metering mechanism from the cement storage hopper into the discharging sand and stone and all three ingredients are then delivered into a elongated mixing trough mounted on the rear of the chassis. Water is added with the materials at the entrance and the ingredients are mixed into concrete in the trough before being discharged from the trough at the job site.
Many advantages and benefits are enjoyed by persons who employ the ZIM-MIXER system in their concrete production business. An important one is that the system permits the formulation and delivery of relatively small batches of concrete which can be used to fulfill orders where only small quantities of concrete are needed, thus obviating the need for taking such quantities from a single large pre-mixed batch. Since only a small portion of the system, the mixing trough, is utilized for mixing the concrete, it can be quickly and easily cleaned after completion of a "mixing" or production operation. Equally important, since the mixing of the concrete is performed "on site", selective variation of the ingredients of the mixture can be readily accomplished and the water content of the mixed concrete can be easily controlled. Finally, in the mixing trough, a positive mechanical mixing action at a desired rate is peformed to assure a uniform dispersal of all the ingredients of the concrete mix.
For the most part, the overall performance of the ZIM-MIXER mobile concrete production system has met and even surpassed expectations over the years. However, from time to time, in any system, and the ZIM-MIXER system is no exception, a need arises to make certain improvements which will solve problems which crop up and to increase performance and productivity even further.